chmod not working on vbox shared folder

http://serverfault.com –
The folder /var/www was mounted during init, using:
mount -t vboxsf cuckoo_shared /var/www/ -o uid=1000,gid=1000,rw,dmode=755
Now, all the files belong to my user jdrummond as default. And also have 755 as default mode.
But now every chmod that I try to run doesn't seem to work:
My doubts on this are:
First: why is my index.php file 777 even when I said it should be 755 on the mount command?
Second: why isn't my chmod working?
Thanks
I've tried to run the chmod command with sudo but it also didn't work.
Virtualbox 4.1.18:
Host = Windows 7
Guest = Ubuntu 11.04.
(HowTos)

I'm running VirtualBox 4.2.18 with a Windows 7 host and Ubuntu 13.10 guest. I'm trying to set up a shared folder, but attempting to read the folder from the Ubuntu VM appears to hang indefinitely. Writing to the shared folder, however, works fine.

On the Windows host, the shared folder is set up to point to C:\ubuntu_share.